> On Fri, May 22, 2020 at 6:20 PM Andy Shevchenko > <andy.shevche...@gmail.com> wrote: > > On Fri, May 22, 2020 at 10:46 AM <dinghao....@zju.edu.cn> wrote: > > ... > > > Moreover, consider below case > > > > CPU1: ...somewhere in the code... > > pm_runtime_get() // with success! > > ...see below... > > pm_runtime_put() > > > > CPU2: ...on parallel thread... > > ret = pm_runtime_get_sync() // failed! > > if (ret) > > pm_runtime_put() // oi vei, we put device into sleep > > > > So, there is a potential issue. > > ...and even if it's impossible (no bugs in runtime PM core, etc) the > code with put() looks suspicious. >
I may understand what you are worried about. Do you mean that executing pm_runtime_put() will influence other threads (e.g., one parallel thread can put the device into sleep while other threads are using this device)? I think this will never happen. Because in this case the PM usage counter cannot be decreased to zero if there are still some threads using this device. Otherwise, pm_runtime_put() should never be used in the case of multithreading, which is strange since this API is used widely. I also checked many other implementation of probe in drivers. It seems that using pm_runtime_put() is ok. If I misunderstood your opinion, please point it out, thanks. Regards, Dinghao > -- > With Best Regards, > Andy Shevchenko
